There are a number of third party services that can take care of exactly this workflow for you. I use Instapaper, but there are others. Fetching RSS feeds and emailing the mobi files to my device is a supported feature. This or a similar service may be easier in the long run than running the conversion process yourself.
– CalebJan 20 '14 at 12:16

@Caleb I know of these services, but so far I do not know of any free services that preserve images and actually subscribe to the feed. In Instapaper every article must be added manually instead of subscribing the feed only once.
– TimJan 20 '14 at 12:25

I don't see what I was looking for now either. There are third party (e.g. Instasciber) and external automaters (e.g. IFTTT) that can make this happen.
– CalebJan 20 '14 at 12:32